All insects are cold-blooded and cannot generate heat from their bodies.
Instead, insects rely on the heat from their surrounding environment to increase their body heat. This heat embodiment allows insects enough time to hunt for food.
While all insects are cold-blooded, they use a variety of different and fascinating ways to maintain a stable body temperature that enables survival.
In this article, we’ll delve into the mysterious world of insects and look at:
- Why are insects cold-blooded?
- Examples of how insects deal with the cold
- How do insects absorb heat?
- Thermoconformer ‘vs’ Thermoregulator
Examples of how insects deal with the cold
Insects struggle to survive in freezing conditions and usually die from the formation of ice crystals within their bodies.
These ice crystals attach to the fluid within their bodies, and as the ice expands, it bursts or destroys the cells, causing an insect to die.
In most cases, insects have built adaptation systems to deal with cold weather. The most common method is to avoid cold weather altogether, called ‘freeze avoidance’.
There are many species of insect that are migratory and will flee freezing temperatures before winter sets in.
Seasonal Migrating insects
Seasonal migration of insects is very common, and insects such as dragonflies, butterflies, and moths are just a few examples of insects that rely on freeze avoidance tactics to mitigate their exposure to damaging freezing weather.
Mass migrations of insects can involve millions of insects and can cover vast distances.
From state to state, or across entire continents, insects will ambitiously and instinctively cover thousands of miles to get their required dose of warmer weather.
The next time you see a dragonfly buzz by, think of it with a little suitcase, heading off for its vacation.
Insects that rely on migratory behavior often have polymorphic forms, such as a caterpillar that transforms into a butterfly or moth.
A good example of this method is used by the Monarch butterfly that migrates south to Mexico in the fall to escape the cold US winter and returns north to warmer weather in the spring.
Burrowing insects such as the Ebony bug (Thyreocoridae) will hide out from the freezing winter conditions by burrowing deep underground where the earth’s temperature remains stable.
Insects such as ants, mining bees, cicadas, and termites are all good examples of insects that will burrow deep into the ground to maintain stable temperatures.
Can insects survive in extreme cold?
With few exceptions, most insects cannot survive below -30 F. Therefore, most insect species have adopted warm tropical climates, allowing them to thrive without the threat of freezing temperatures or risky migration.
Warm, damp regions along the equator such as the Amazon in Brazil, Central ; South America, and Asia make for fertile ground, with plenty of access to heat and moisture that’s prime territory for laying larvae.
One fascinating example of an insect that can survive extremely cold conditions is the Antarctic Midge. This creative little critter is often referred to as the sole survivor of Antarctica, as it is the only insect or animal that lives in Antarctica year-round.
It does so by producing large amounts of sugar in its cells, reducing the freezing point of liquids. At the same time, these insects burrow into the freezing soil, allowing the soil to extract almost all the water from its body.
With a sugar high and virtually no water in its body, the Antarctic Midge is impervious to freezing, simply because it is completely dehydrated and, hence, cannot be affected by the formation of ice crystals in its cells.
Other types of freeze-resistant insects
Some insects can produce a substance inside their bodies that allow them to survive all through a freezing winter.
One of the most fascinating examples is the Woolly Bear Caterpillar, which lives around 90% of its life in a frozen state. These amazing creatures are commonly found all over the northern regions of the US and can adapt to freezing conditions, surviving a whole winter.
Insects such as the Wooly Bear Caterpillar actually do freeze during winter. However, they produce an ice-nucleating protein called glycerol inside their bodies, which works similarly to the chemical antifreeze.
Glycerol prevents the internal cells inside their organs from completely freezing and allows them to survive extreme winter conditions.
Woolly Bear Caterpillars can survive an entire winter in this state, even surviving temperatures as low as -90 F.
Come Spring, the outdoor temperature increases, the Woolly Bear Caterpillar thaws and then builds a cocoon, undergoing a process of metamorphosis.
Several weeks later, the caterpillar has undergone a complete transformation and emerges from the cocoon as an Isabella Tiger Moth.
How do insects know when winter is coming?
Being cold-blooded, insects really need to know when to skip town before the first flake of snow hits the ground. The way they do so is called “Diapause” and this is an adaptation passed on over generations, allowing insects to gauge when the weather is about to turn.
Surprisingly, temperature plays little concern to an insects’ ability to use diapause. Instead, they rely on the reducing amount of daylight which signals to the insect’s body that it’s time to prepare for dormancy.
As global warming continues to push back the beginning of fall, insects defer their instinct to trigger diapause, causing confusion and often resulting in insects thinking it is a symbol of spring or summer. Sadly, once winter strikes, they bear the full brunt and often are unprepared.
Why are insects cold-blooded?
Insects’ blood is very different compared to the blood of humans, and it goes far beyond the simple explanation of being warm versus cold-blooded creatures. Insect blood is a yellow or greenish color and flows within the main body cavity of the insect.
Most insects and other invertebrates only use blood to feed their main central organs.
Their blood is pumped by their heart around their body cavity, their limbs and extremities use a fluid (hemolympha heterogeneous) that lubricates all of their internal tissues.
The warmer the hemolymph fluid becomes due to the absorption of heat from the environment, the more agile the insect will be.
How do insects absorb heat?
Although all insects are cold-blooded, they generate heat in different ways. There are two types: exothermic or endothermic insects. Both varieties of insects achieve thermoregulation in different ways, maintaining a stable body temperature so they can hunt for food and survive.
Ectothermic insects cannot produce heat from their bodies and therefore must absorb heat from the sun and environment they interact with to gather enough heat to survive.
Ectotherms are often tiny insects with a low metabolic rate and can adapt and absorb even very subtle temperature changes from their environment. They will seek an environment to suit their temperature needs, either from the sun or shade.
Endothermic insects rely on bio-chemical body movements such as flying to develop heat. They have a far higher metabolic rate because of the need to burn a lot of energy to maintain their body temperature.
Endothermic insects can either walk or fly, although walking does little to generate the heat required for critical stages of activity. Flying, however, generates enormous stimulation of the muscles and produces significant amounts of heat, which can be temporarily stored following an activity.
While endotherms can produce heat within their bodies, they are still cold-blooded and always need to remain cautious about absorbing too much heat from their environment.
If a flying insect were to fly too close to an external heat source, it would need to regulate its temperature to stay in its temperature comfort zone. This process is called thermoregulation.
Thermoconformer versus thermoregulator
Insects are typically considered to be capable of thermoregulation, although there are some species of insect that can be either thermoconformers or thermoregulators.
Insects that rely on thermoregulation to maintain body temperature use different methods, either producing heat within their bodies or by using their environment to absorb the required temperature.
Insects that are thermoconformers allow their body temperature to fluctuate within a certain temperature comfort zone. This is how some insects can survive colder temperatures than others.
While all insects are cold-blooded, they have found ingenious ways to maintain or generate heat, from simply migrating to warmer climates once the mercury drops, to sophisticated scientific techniques that dehydrate their bodies while boosting proteins and sugars in their bodies, allowing them to create an organic antifreeze.
Insects are fascinating creatures, capable of feats many consider far greater in evolutionary development when compared to the evolution of other species.
They are capable of adapting to even the most severe conditions and have developed intriguing methods to survive at all costs.
Next time you pass a slow beetle crawling along the ground or a fast-flying insect buzzes by, give some consideration to why it’s doing what it is. It could be on a slow but important mission to find shade or sun. On the flip side, it could be darting across the sky to generate heat or fly off to an exotic land.
Alright, that’s it for this article, here are a few hand-selected articles that you might also find interesting reads:How Do Bugs Walk On Walls?! The Curious Answer
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